In the design and operation of envelope making machine every effort is made to speed up the machine and to prevent shut downs during the working day. This is true in envelope making as in other industries, mainly because the envelope machine represents a large capital investment whose time should always be used where at all possible in the production of envelopes, and furthermore, in which as many envelopes as possible are produced in a unit time. Not only does the capital cost of the machine enter into this, but also the cost of labor for the operator. One problem that has constantly inhibited the speed up and continuous operation of those envelope making machines which specialize in window-type envelopes, is that the equipment which applies gum to the envelope blank before the window is applied continues to operate even in those instances when an envelope is missing. This means the roller on which the envelope blank normally would be carried would receive a layer of gum which would in turn be applied to subsequent envelope blanks and this would cause a sticking and disruption of operation further on downstream in the machine. To prevent this, it has been necessary to provide a complex and troublesome water box apparatus to wash the roller. Furthermore, difficulty would also be experienced in those machines when an envelope blank is missing because of the fact that the apparatus which introduces the windows dispenses a window even when the envelope blank is missing. This means that a window without an envelope would appear downstream in the machine and cause disruption of the subsequent operations. For that reason, it has been necessary to provide a vacuum roller underlying the window dispensing roller and this roller must be carefully adjusted at all times both sideways and lengthwise. In general, the problem of the gum applicators operating when an envelope blank is missing from the stream is common to all envelope making machines as is the problem of windows being introduced without an envelope blank; although devices have been designed and used in the past to skip the gumming operation when an envelope blank is missing and to remove the loose windows when a window is missing, the equipment has been cumbersome and slow in operation, thus slowing down the speed of the envelope machine. Furthermore, the complications of the mechanism introduced has made it difficult to adjust the gum applicator and the window dispenser when the type of envelope being made is changed. These and other difficulties experienced in the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide an envelope machine in which the gum is not picked up or applied when an envelope blank is missing, thus greatly simplifying the apparatus and making the machine easier to adjust.
Another object of this invention is the provision of an envelope machine having simple means for removing a window patch from the stream when its presence is likely to produce mis-operation of the machine.
A further object of the present invention is the provision of simple apparatus for producing window-type envelopes in which means is provided to prevent disruption of machine operation due to an envelope blank being missing from the stream.
It is another object of the instant invention to provide an envelope machine of trouble-free nature for producing windowed envelopes in which the window gum is not applied when an envelope blank is missing from the stream.
A still further object of the invention is the provision of an envelope machine of simple construction for producing windowed envelopes in which, when an envelope blank is missing from the stream, the window which normally would be applied to the missing envelope blank is removed from the stream.
It is a further object of the invention to provide an envelope machine in which gum is not supplied to any parts of the machine adjacent the envelope-making portions when an envelope blank is missing from the stream.
It is a still further object of the invention to provide an envelope machine of simple and trouble-free construction in which disruption of machine operation due to gumming of parts and the presence of an excess window patch is avoided.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.